Low octane causing anyone else problems?

barbaram · 08-23-2006, 11:39 PM

I have been wondering about this. while states are responsible for auditing the accuracy of pumps, who watches the octane ? is it possible for the octane rating to be a bit lower than it should be? would this cause a decrease in mileage?
In my old cars I would use a tank of the mid gas once in a while.....

tomdeimos · 09-29-2006, 02:13 PM

I am now convinced I have had low octane tank fillups causing most of my fuel related low mpg tanks. But it has not happened again.

I have been experimenting with octane grades and watching the canview and the effects are very visible.
Normal cruise is not showing any noticable difference with fuel and spark advance tends to stay at 29 to 32 degrees.

With acceleration I estimate at say 40 mph and warmed up I can accelerate with up to 60% throttle with an 87 octane tank, before the knock sensor retards. With 89 octane it goes to more like 75% before this happens.

When the sensor triggers it retards drastically going from maybe 38 to 42 deg advance down to 27 degrees. Once this happens it stays retarded till you stop accelerating and then resume more gently.

Seems like regular 87 octane is OK for high mpg drivers but not for agressive drivers. If a tank is just a little lower than spec like 85 octane, it would have a noticable impact on most drivers mpg.

MPG impact of octane would be more important in city driving and in mountains than normal highway driving.

My experiments here were all with Shell gasoline. I've used a couple of tanks of 93 octane too with no problems or mpg drop, but that was before I started watching the spark advance readouts.

I'm going back to regular now, but will put in premium with a partial fill up anytime I see the spark retard happening more than normal.

I was going to try to compare mpg too this time, between the 87 and 89 octane, but our early swtch to winter fuel killed that idea. My mpg is down close to 5 mpg now in my regular commuting. I wll get much of this back after this weekend, as I will winterize and start using my block heater for the winter.

DaveinOlyWA · 10-20-2006, 10:19 AM

sorry, cant believe your statement. is it a coincidence that MA is one of the states with stricter air polution guidelines and PA is not??

i think not. there has been a million studies over the impact of high octane gas in a car that does not require it and there has never been any evidence shown that disputes the statement that you are wasting your money by buying it.

but that is ok. keep reporting back. any final conclusion made with the amount of data you have might be a bit premature. in time, i think your high octane MA gas will perform just as your low octane MA gas does.

for me, i can drive to Idaho and get better performing gas (actually i went to Montana but if i didnt feel like driving as far). i too averaged 56 mpg on a trip averaging about 70 mph coming home. same trip going out with WA gas ....51.5 see a corellation here??

tomdeimos · 10-20-2006, 11:41 AM

<div class='quotetop'>QUOTE(DaveinOlyWA @ Oct 20 2006, 11:19 AM) [snapback]335556[/snapback]</div>

Quote:

sorry, cant believe your statement. is it a coincidence that MA is one of the states with stricter air polution guidelines and PA is not??

i think not. there has been a million studies over the impact of high octane gas in a car that does not require it and there has never been any evidence shown that disputes the statement that you are wasting your money by buying it.

but that is ok. keep reporting back. any final conclusion made with the amount of data you have might be a bit premature. in time, i think your high octane MA gas will perform just as your low octane MA gas does.

for me, i can drive to Idaho and get better performing gas (actually i went to Montana but if i didnt feel like driving as far). i too averaged 56 mpg on a trip averaging about 70 mph coming home. same trip going out with WA gas ....51.5 see a corellation here??
[/b]

Not sure what you don't believe.

1 I do get great regular gas in MA most of the time, and that is what I normally use.
2 Premium bought in MA works great too. So due to both of these, the issue is not PA vs MA fuel I think.
3 CAN VIEW clearly shows when the octane is not enough. If it retards the spark for normal acceleration that is inadequate octane by definition.
4 I now check the spark advance on every tank, but I have not had another problem tank since, and no unexplained low mpg tanks either since my trip.

dmckinstry · 10-20-2006, 01:37 PM

<div class='quotetop'>QUOTE(DaveinOlyWA @ Oct 20 2006, 08:19 AM) [snapback]335556[/snapback]</div>

Quote:

sorry, cant believe your statement. is it a coincidence that MA is one of the states with stricter air polution guidelines and PA is not??

i think not. there has been a million studies over the impact of high octane gas in a car that does not require it and there has never been any evidence shown that disputes the statement that you are wasting your money by buying it.

but that is ok. keep reporting back. any final conclusion made with the amount of data you have might be a bit premature. in time, i think your high octane MA gas will perform just as your low octane MA gas does.

for me, i can drive to Idaho and get better performing gas (actually i went to Montana but if i didnt feel like driving as far). i too averaged 56 mpg on a trip averaging about 70 mph coming home. same trip going out with WA gas ....51.5 see a corellation here??
[/b]

Yes, I do. I believe it's due to elevation change. I get lower mileage traveling from Olympia to Spokane than I do from Spokane to Olympia as well. My mileage goes up dramatically after reaching Snoqualmie summit heading west. By the time I get to Olympia I've more than made up the drop in mileage lost between Spokane and Snoqualmie.

Dave M.

Pinto Girl · 10-20-2006, 02:55 PM

<div class='quotetop'>QUOTE(Tempus @ Aug 14 2006, 02:33 PM) [snapback]303149[/snapback]</div>

Quote:

That's really not possible.

No Octane boosting additive that I know of has more specific energy than gasoline. 99.99% of them (I won't say 'all' just to be covered), have less.

What is poossible is that the 'mix' of oxygenates varied in the two locations. The US requirements for oxygenate mixes are an insane crazy-quilt. Maybe your initial tank was 10% ethanol, and your second wasn't.

The only possible way that a higher octane gas could give better mileage in a Prius is if you were running crap gas and had some deposit buildup that the detergent in 'quality' gas cleaned.

That's why the Top Tier gas program where manufacturers pledge to put decent detergent packages in all grades is so important.

Plus, high octane gas will damage the emissions control system in the Prius because it does burn less efficiently and dumps unburned gunk into the cats.

You can research all over the place and NO reputable source will ever tell you that you'll get higher mileage with high octane in an engine designed for regular. Just isn't going to happen.

If deposits are your problem, buy a better class of Regular or dump a bottle of Techron in with every oil change.
[/b]

I think you put this very well.

I've also read that actually, high octane fuel burns less well than regular.

The idea with premium (higher octane) fuels is that they permit higher compression without preignition; the octane is actually keeping the fuel from burning, not providing additional energy.

The level of oxygenation or other variations in the fuel blend is probably at the root of what you're experiencing.

tripp · 10-20-2006, 05:45 PM

I'm probably using lower octane than most folks in the states. Here in Denver "regular" gasoline is 85 octane. That's what I use and I've had no problems nor noticed any pronounced drop in MPG.

tomdeimos · 10-21-2006, 02:24 PM

You folks are all stating correct info but still neglecting my main points.

1 Octane that is too low causes the spark advance to retard and stay retarded for some time.
This drastically cuts mpg and dwarfs any energy differences.

2 I happily burn regular fuel most of the time. All I am saying is when I buy regular it is not always up to the specs for regular. I believe that is the primary cause of my tanks that have had unexplained low mpg. The other cause would be differing amounts of ethanol and or water in the fuel.

3 The can view works very well to detect any octane issues if and when they occur.

dmckinstry · 10-22-2006, 09:01 AM

<div class='quotetop'>QUOTE(tripp @ Oct 20 2006, 03:45 PM) [snapback]335872[/snapback]</div>

Quote:

I'm probably using lower octane than most folks in the states. Here in Denver "regular" gasoline is 85 octane. That's what I use and I've had no problems nor noticed any pronounced drop in MPG.
[/b]

But of course, 85 octane is the correct rating for higher altitudes. It does for you in Denver what 87 does at sea level.

Dave M.

jroth74 · 12-04-2006, 02:56 PM

Here is something to think about when deciding what brand of gas to buy. We drive hybrids and get the best mileage available, no matter what brand we buy. The incentive for me is where does the oil come from. Further more, not contributing money to terrorist and the oil tycoons (Bush) who are causing hell on earth in the Middle East is the #1 reason I bought a Prius. There is a lot of mixed info on who really sells Middle East oil, but some companies have proven not to. Do the world another favor (1st one is driving a Prius) and find out where you can buy Satan free gas in your area.

http://urbanlegends.about.com/librar...oycott-oil.htm

10-20-2006, 10:19 AM	#23
DaveinOlyWA 3rd Time was Solariffic!! Join Date: Apr 2004 Location: South Puget Sound, WA Posts: 12,812 My Car: 2010 Prius Model: IV Package: Solar Roof Thanks: 38 Thanked 187 Times in 160 Posts Friends: 12	sorry, cant believe your statement. is it a coincidence that MA is one of the states with stricter air polution guidelines and PA is not?? i think not. there has been a million studies over the impact of high octane gas in a car that does not require it and there has never been any evidence shown that disputes the statement that you are wasting your money by buying it. but that is ok. keep reporting back. any final conclusion made with the amount of data you have might be a bit premature. in time, i think your high octane MA gas will perform just as your low octane MA gas does. for me, i can drive to Idaho and get better performing gas (actually i went to Montana but if i didnt feel like driving as far). i too averaged 56 mpg on a trip averaging about 70 mph coming home. same trip going out with WA gas ....51.5 see a corellation here?? __________________ My Blue 2010 : Last tank 548.4 @ 50.48 pump (56.5 MFD) 5.74 CPM, 23 MPH, Lifetime:8102.4 miles MPG pump. 53.75 (59.49 MFD) 5.04 CPM. Summer MPG 57.4 Winter: 48.98 My 2006 SPM: Last tank 456.3 @46.9 pump (47.3 MFD) 6.23 cpm winter mpg 49.29 summer mpg 53.41 lifetime: 44,804.8 miles 51.18 mpg pump (52.34 mpg MFD) 5.54 cpm My 2007 Zenn total "fuel cost" $168.25 on "about" 9659.7 miles. 1.74 cents per mile (granted i plug in for free at work!!) My Plate: DUALPWR (Dual Power)

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08-23-2006, 11:39 PM	#21
barbaram Senior Member Join Date: Jan 2006 Location: Trenton, NJ Posts: 826 My Car: 2010 Prius Model: IV Package: Solar Roof Thanks: 28 Thanked 12 Times in 8 Posts Friends: 0	I have been wondering about this. while states are responsible for auditing the accuracy of pumps, who watches the octane ? is it possible for the octane rating to be a bit lower than it should be? would this cause a decrease in mileage? In my old cars I would use a tank of the mid gas once in a while.....

09-29-2006, 02:13 PM	#22
tomdeimos Join Date: Feb 2004 Location: Lexington, MA Posts: 995 My Car: Model: Package: Thanks: 0 Thanked 0 Times in 0 Posts Friends: 0	I am now convinced I have had low octane tank fillups causing most of my fuel related low mpg tanks. But it has not happened again. I have been experimenting with octane grades and watching the canview and the effects are very visible. Normal cruise is not showing any noticable difference with fuel and spark advance tends to stay at 29 to 32 degrees. With acceleration I estimate at say 40 mph and warmed up I can accelerate with up to 60% throttle with an 87 octane tank, before the knock sensor retards. With 89 octane it goes to more like 75% before this happens. When the sensor triggers it retards drastically going from maybe 38 to 42 deg advance down to 27 degrees. Once this happens it stays retarded till you stop accelerating and then resume more gently. Seems like regular 87 octane is OK for high mpg drivers but not for agressive drivers. If a tank is just a little lower than spec like 85 octane, it would have a noticable impact on most drivers mpg. MPG impact of octane would be more important in city driving and in mountains than normal highway driving. My experiments here were all with Shell gasoline. I've used a couple of tanks of 93 octane too with no problems or mpg drop, but that was before I started watching the spark advance readouts. I'm going back to regular now, but will put in premium with a partial fill up anytime I see the spark retard happening more than normal. I was going to try to compare mpg too this time, between the 87 and 89 octane, but our early swtch to winter fuel killed that idea. My mpg is down close to 5 mpg now in my regular commuting. I wll get much of this back after this weekend, as I will winterize and start using my block heater for the winter.

10-20-2006, 05:45 PM	#27
tripp Which it's a 'ybrid, ain't it? Join Date: Oct 2005 Location: Denver, CO Posts: 4,341 My Car: 2005 Prius Model: Package: #3 Thanks: 3 Thanked 7 Times in 5 Posts Friends: 6	I'm probably using lower octane than most folks in the states. Here in Denver "regular" gasoline is 85 octane. That's what I use and I've had no problems nor noticed any pronounced drop in MPG.

10-21-2006, 02:24 PM	#28
tomdeimos Join Date: Feb 2004 Location: Lexington, MA Posts: 995 My Car: Model: Package: Thanks: 0 Thanked 0 Times in 0 Posts Friends: 0	You folks are all stating correct info but still neglecting my main points. 1 Octane that is too low causes the spark advance to retard and stay retarded for some time. This drastically cuts mpg and dwarfs any energy differences. 2 I happily burn regular fuel most of the time. All I am saying is when I buy regular it is not always up to the specs for regular. I believe that is the primary cause of my tanks that have had unexplained low mpg. The other cause would be differing amounts of ethanol and or water in the fuel. 3 The can view works very well to detect any octane issues if and when they occur.

12-04-2006, 02:56 PM	#30
jroth74 Join Date: Nov 2006 Posts: 3 My Car: Model: Package: Thanks: 0 Thanked 0 Times in 0 Posts Friends: 0	Here is something to think about when deciding what brand of gas to buy. We drive hybrids and get the best mileage available, no matter what brand we buy. The incentive for me is where does the oil come from. Further more, not contributing money to terrorist and the oil tycoons (Bush) who are causing hell on earth in the Middle East is the #1 reason I bought a Prius. There is a lot of mixed info on who really sells Middle East oil, but some companies have proven not to. Do the world another favor (1st one is driving a Prius) and find out where you can buy Satan free gas in your area. http://urbanlegends.about.com/librar...oycott-oil.htm